Founders Martin Eberhard and Marc Tarpenning tell the story of the early days at Tesla Motors

Elon Musk is the most famous CEO of Tesla. But Martin Eberhard and Marc Tarpenning founded the company in 2003 and were the original executives. CNBC sat down with them to talk about the idea for Tesla Motors, the battery, Elon Musk and building its first car, the all-electric Roadster.